Abstract:

The study aims to clarify the process of arable land loss caused by loess slope instability, in which the loess slope stability was changed by irrigation water infiltration into soil and loess under large-scale agricultural irrigation. On the basis of statistical analysis of the loss area of arable land, the farmland area under irrigation, the number of geological disasters and the proportion of farmland loss caused by geological disasters in Tianshui of Gansu, the author collected samples of undisturbed soil and loess from typical stratigraphic sections, and tested the physical and mechanical properties and shear strength of soil under natural condition and irrigation. The slope stability was quantitatively analyzed by Swedish method based on limit equilibrium method in combination with Lizheng rock slope stability analysis system. The results showed that the slope was steady and its stability coefficient was 1.074 under natural condition, but under agricultural irrigation, with the increase of water infiltration depth, the stability coefficient decreased gradually, and the slope became unsteady. If farmland irrigation only saturated the soil layer, it would have little effect on the stability of the slope. When the thickness of loess saturated layer was greater than 2 m due to continuous irrigation water infiltration, the slope stability would be reduced by one level and became unsteady. When the thickness of loess saturated layer was greater than 10 m, the slope would be unsteady and landslides would develop, causing arable land loss.

Key words: agricultural irrigation, soil, arable land, loessal soil, loess slope, slope stability